Process for desulphurizing hydrocarbons



Patented Mar. 30, 1937 I UNITED STATES PATENT OFFICE PROCESS I FOR DESULPHURIZING HYDROCARBONS Albert E. Bucll and Walter A. Schulze, Bartlesville, kla., assignors to Phillips Petroleum Company, Bartlesville, 0kla., a corporation of Delaware 7 Claims. (Cl. 19628) This application is a division of our co-pending application, Serial No. 616,574, filed June 10, 1932, entitled Processes for desulphurizing hydrocarbons, wherein it is shown that certain minerals constitute effective contact agents for the vapor phase desulphurization of hydrocarbons by which a part of the organically combined sulphur is eliminated as hydrogen sulphide.

This invention relates to processes for treating sulphur bearing hydrocarbon mixtures such as natural or refinery gases, the naphtha derived from the distillation or cracking of petroleum, oil shale distillates, and other hydrocarbon products from which the removal of certain sulphur compounds is desired. 1

More specifically it relates to the partial desulphurization of straight run and cracked gasolines, to which the process is particularly applicable, and the following disclosure will be limited to this application of the process for the sake of simplicity, but it will be understood that a similar procedure is followed in treating the other hydrocarbons mentioned.

To meet the specifications for motor fuel with respect to sulphur content, distillates from high sulphur petroleum require a drastic treatment for sulphur removal. It is well known that the method in most common use at present is objectionable from the standpoint of losses in volume and quality of product, as well as of excessive cost.

To overcome these objections, processes have been devised for sulphur removal which are based on the known catalytic action of certain contact agents on sulphur compounds in the vapor phase at elevated temperatures, in which the sulphur is eliminated as hydrogen sulphide. The present invention is an improvement of processes of this type, particularly with respect to the nature and preparation of the contact agents employed.

The catalysts proposed by previous investigators are metals; or oxides or sulphides of metals. Metals known to be hydrogenation catalysts have a limited usefulness in a. process primarily employed to eliminate sulphur rather than to obtain hydrogenation effects, because of their ability to cause rapid decomposition of hydrocarbons under the operating conditions with accompanying-deposition of carbonaceous residues and consequent poisoning of the catalyst. Therefore, metallic sulphides, oxides, or oxides convertible to sulphides during the desulphurization process are advantageously employed, as

their action is more exclusively confined to the sulphur impurities in the hydrocarbons.

The oxides and sulphides mentioned, which are used in desulphurization processes, are at present synthetically prepared as more or less pure compounds, and are often deposited upon or admixed with more or less inactive carriers. The use and preparation of these synthetic substances is unduly expensive, and such catalysts usually have no salvage value when their usefulness as contact agents has been outlived.

Undoubtedly it is for these reasons that the genv eral adoption of catalytic desulphurization processes, the principles of which have been long and widely known, has been so unduly delayed. Another disadvantage of the synthetically prepared agents is that their usual form is a finely precipitated powder, which is inconvenient to handle, diflicult to maintain in a reaction chamber thru which gases are moving at a high velocity, and which tendsto pack and produce a high back pressure if it cannot be incorporated in a suitable carrier.

The primary object of this invention is to provide a novel catalyst for use-in processes for desulphurizing hydrocarbons containing organic sulphur compounds as impurities, the sulphur being eliminated in the form of hydrogen sulphide, wihch catalyst overcomes the several objections, previously enumerated, to the specially prepared catalysts used by previous investigators.

We have found that certain naturally occurring substances, containing compounds of the class mentioned above as contact agents, maybe used substantially in their'original state as catalysts.

These substances are relatively inexpensive compared to the corresponding synthetic compound. Moreover, their natural form is in many ways superior to the synthetic form, as the natural crystals or lumps of these substances may be easily reduced by crushing to a convenient and eflicient size for contact purposes as contrasted with the powdery form of the synthetic compound. Furthermore, the natural substance is often as efilcient, or even more so (in proportion to the percentage of active element present) as the prepared agent.

The naturally occurring substances referred to are metallic minerals or ores of these minerals which consist of oxides and sulphides of the metals whose oxides are grouped as dehydration and dehydrogenation catalysts, e. g., aluminum, tungsten, vanadium, chromium, cadmium, zinc,

molybdenum, etc. Examples of these minerals are chromite, vanadinite, molybdenite, molybdite, descloizite, woliramite, bauxite, etc.

Temperatures of the order or 500-800 F. are usually necessary, depending on (1) the particular mineral used as catalyst, (2) the time of contact between the petroleum product and the catalytic material, and (3) the specific properties of the hydrocarbon vapor which is being desulphurized. Temperatures of 000-700 F. are usually preferred when straight run naphthas or cracked distiilates are the products undergoing treatment. High pressures are not needed, extremely good results being obtained at atmospheric pressure. In practice it is usually desired to use pressures somewhat above atmospheric so that the vapors can be directly conducted to a i'ractionator or to treating tanks for final processing. This conversion of the organic suiphureompounds to hydrogen sulphide may be accompanied by dehydrogenation of some of the hydrocarbons present, depending on the particular catalyst and the temperature used. I

The presence of hydrogen gas in the sulphur bearing petroleum vapor aids in the conversion of the sulphur compounds to hydrogen sulphide when certain of the minerals, tor example,

vanadinite. are used as catalysts. Hydrogen sul-.

phide (in small quantities) and inert gases along with the petroleum vapor apparently make little diil'erence in the amount of desulphurization which can be obtained in-one passage over the mineral catalyst.

heated vapors thru a bed of catalytic material maintained at an elevated temperature, say 700 5 cataLvtic material may comprise one or more of the minerals set forth, crushed to a suitable size, usually -00 mesh, and possibly concentrated or diluted according to its activity. Diluents may comprise naturally associated active and/or inactive substances or substanceswhich are suitable i'or diluting purposes altho not natural associated with the catalytic material. E'mample I.Vapors of a sour cracked gasoline containing 0.142% sulphur were passed over a catalyst comprising a crushed ore (30-60 mesh) containing the minerals vanadinite and descloizite at a temperature of 700 F. and a rate such that the contact time was about two seconds. The resulting product was sweet, indicating that so the mercaptans present had been completely converted, and had a sulphur content 01' 0.089%.

The same catalyst also eflected a reduction of sulphur content of from 0.091% to 0.034% and completely sweetened a sour straight run naphtha at the same temperature and flow rate. Example lI.-Chromite crushed to 30-60 mesh and maintained at a temperature of 700 1". was used as the catalyst. Vapors of a sour straight run naphtha were passed over at a rate to produce a contact time of about two seconds with an eil'ect identical to that described in the previous example. Prolonged passage of this product over the catalyst failed to produce an appreciable change in its activity. In the next run over the samecatalyst, 10% by volume'oi butyl sulphate solution. After severe pi A typical process for desulphurization of cracked gasoline consists in passing the super- The condensed vapors are then mercaptan was added to the naphtha. The enormous sulphur content of this product was completely converted to hydrogen sulphide. as shown by testing the condensate with cadmig: catalyst, it was no longer able at'the flow rate, to produce a completely sweet product. but was'stiil capable of eii'ecting a very satisfactory sulphur reduction, about 45%, in naphthaa oi usual sulphur content, and the products were only very slightly sour. The catalyst was kept in continuous operation tor a period or seven days after the buty'imercaptans solution was passed over it, during which time a total or about 700 volumes (liquid) of gasoline was treated. The sulphur reduction on the final sample was substantially the same as that on the first sample, 1. e., about 45% or the sulphur originally present.

Example "I.Vapors or a sour cracked gasoline containing 0.18 per cent sulphur were passed over a cataiystcomprislng a crushed cm (40-60 mesh) containing the mineral woiiramite at a temperature or 700' I". and at a rate such that the contact time was about 8 seconds. The resulting product, after removalot hydrogen sui-,

phide, was doctor sweet. indicating that the mercaptans present had been completely converted. Its sulphur content was reduced to 0.005 percentbythiscatalytic treatment.

The same catalyst reduced the sulphur content 01' a sour straights gasoline from 0.000 percent to 0.020 per centat about the same temperature and flow rate Alter removal or the hydrogen sulphide the gcsoime was-doctor sweet.

While it is possible to operate this. process in such a way that a gasoline is obtained as in Example. lrdescribedabovc. it is not meant to be con'strued'that such a product is always-obtained in actual 11mm 1. The process of deniphurinng petroleum -131- drocarbon fluid containing manic sulphur comp unds as impurities. comprising heating the fluid in the vapor state to a temperature within the range of 500 to 800.. 1" contacting the "mat substantially. the same temperature with a catalyst consistingorcrudemineralorecontaininga substantial proportion of a tungsten comma. whereby the organic sulphur compounds are decomposed in ahydr gcn hilphide. and

she hydrogen sulphide hydrocarbon llld.

2. 'lheprocessoipetrol'eumotl with a boiling point lower than the end point or kerosene, comprising vaporizing the oil. superheating the vapors containing organic niphur compounds to a temperature within the ranged 500 to 800 E, contacting the vapors at'euhstantially the sametemperatureior a period or about 2to l0secondswithatmnlnineralcam whereby the organic sulphur compounds are.de-' composed into hydrogen sulphide, and se the hydrogen sulphide from the oil.

3. The process or desulphurizing gasoline containing organic sulphur compounds as impurities, comprising vaporizing the gasoline, superheating the vapors to a temperature within the range of about 600 to 800 F., contacting the vapors for a period of about 2 to seconds with a catalyst consisting of crude mineral ore containing a substantial proportion of a tungsten compound, and separating the decomposed sulphur 10 impurities from the gasoline.

4. The process of sweetening gasoline containing mercaptans as impurities, comprising vaporizing the gasoline, superheating the vapors to a temperature within the range of 600 to 800 F.,

contacting the vapors for a period of about 2 to 10 seconds with a catalyst consisting of crude mineral ore containing a substantial proportion of a tungsten compound, whereby the mercaptans are decomposed into hydrogen sulphide, separatmg the hydrogen sulphide from the gasoline, and

thereby obtaining a sweetened gasoline.

5. The process of desulphurizing petroleum oil containing organic sulphur compounds as impurities, said oil having a boiling point lower than the end point of kerosene, comprising vaporizing the oil, superheating the vapors to a temperature within the range of 500 to 800 F., contacting the vapors at substantially the same temperature for a period of about 2 to 10 seconds with a catalyst consisting of wolframite ore, and separating the decomposed sulphur impurities from the oil.

6. In a process of desulphurizing gasoline in the vapor state, the steps which comprise superheating the vapors to a temperature within the range of about 600 to 800 F., contacting the vapors at substantially the same temperature for a period of about 2 to 10 seconds with a catalyst consisting of wolframite ore, and separating the decomposed sulphur impurities from the gasoline.

7. The process oi! desulphurizing petroleum hydrocarbon gases containing organic sulphur compounds as impurities, comprising heating the gases to a temperature within the range of 500 to 800 F., contacting the gases at substantially the same temperature with a catalyst consisting of crude mineral ore containing a substantial proportion of a tungsten compound, whereby the organic sulphur compounds are decomposed into hydrogen sulphide, and separating the hydrogen sulphide from the hydrocarbon gases.

ALBERT E. BUELL. WALTER A. SCHULZE. 

